emptying a vector

I have a vector myVector which is declared as a protected member.
my vector is defined a sfollows/.
std::vector < std::vector < double > > myVector.
After I resized this vector, I store ceratin values. Then I want to clear this and store different values.
I did myVector.clear();
But it does not become empty and I get a segmentation fault.
I also try to clear the vector inside and tehn do clear on my vector.
I get a segmentation fault.
I guess may be teh problem is because it is a member of the class.
Any suggestions?
Thanks,
lalitha.V